Coxiella burnetii in Minas and Coalho raw milk artisanal cheese and possible spatial associations with human exposure in Brazil: a cross-sectional study

Abstract

Q fever is a zoonotic disease that occurs worldwide; it is caused by Coxiella burnetii, which infects a wide variety of vertebrate and invertebrate animals, including humans. Domestic ruminants are considered the primary natural reservoir of C. burnetii. Human infection occurs mainly via aerogenic routes, with the ingestion of raw milk being a less common but non-negligible pathway. The aim of this study was to conduct a randomized survey to evaluate the frequency of C. burnetii-positive raw milk artisanal cheese (RMAC) in five traditional Brazilian regions. Additionally, we analyzed the relationships between spatial clusters of C. burnetii-positive RMAC and those of human exposure, livestock concentration, and other RMAC characteristics such as ripening time and microbiological attributes. From October 2017 to April 2018, we collected 100 RMAC samples from different rural family-based cheese-processing agroindustries in four regions of the state of Minas Gerais and one in the state of Piauí. DNA was extracted from RMAC, and PCR was performed using specific oligonucleotides targeting the IS1111 gene. We assessed possible associations between descriptive variables and C. burnetii-positive RMAC, and conducted spatial analyses of rural family-based cheese-processing agroindustries with positive RMAC, human exposure data, and livestock concentration. C. burnetii DNA was detected and sequenced in 25 RMAC samples (25.0 %; 95 % CI: 16.8–34.6 %) from two types of ready-to-eat Brazilian RMAC. The rates of C. burnetii-positive RMAC across the five regions analyzed were heterogeneous (P = 0.04). These rates exhibited a direct linear relationship with ripening periods above the median duration (i.e., 10 days), and an inverse relationship with the time since recognition as traditional cheese-producing regions by the state's official surveillance body. These findings emphasize the need for Good Agricultural and Manufacturing Practices, as well as quality control of RMAC. Finally, we identified potential links between a high-density cluster of human exposure to C. burnetii and clusters of both C. burnetii-positive RMAC and high livestock concentrations, supporting the need for monitoring temporal and spatial trends, conducting risk analyses and genotyping studies, in order to establish control measures with One Health approaches.